This invention relates to the production of texturized yarns or like multifilament groups of synthetic polymeric materials, e.g. tows, and more particularly to an apparatus and process for texturizing yarn to provide uniform random crimps in the filaments of the yarn by pneumatically conveying the yarn into a bulking chamber to form an elongated uniformly compacted yarn mass and to the yarn products resulting from the process.
Heretofore, many apparatus and processes have been developed for texturizing yarn made of thermoplastic polymeric materials by the use of fluid jets or like pneumatic means. Many of these prior developments have been relatively successful in providing bulky voluminous yarn having a degree of crimp uniformity and improved dyeing characteristics suitable for use in the production of textile fabrics, carpets and the like. However, the apparatus employed for carrying out many of these known processes is complex and requires elaborate machining techniques to produce. This apparatus is costly and for this reason less elaborate and slower stuffer box crimping systems, wherein relatively straight feeder yarn is forced into a compression chamber by a pair of driven rolls and is accumulated within the chamber by pressure developed within the chamber, are often employed. In these systems the feeder yarn forms wads of yarn in the compression chamber and a regular crimp is imparted to the individual filaments of the yarn during this accumulation. Also heated fluids such as steam or hot air are often utilized to moisten and/or heat-set the yarn while in a crimped state within the compression chamber.
Because of the advantages found in the yarns produced by the pneumatic bulking or texturizing systems, particularly the high yarn processing speeds, and random crimping of the filaments, the difficulties in producing the necessary apparatus as well as the complex controls required for operating such apparatus have been accepted by the industry. In these known processes an initially straight and pre-drawn yarn which may be untwisted or slightly twisted is subjected to a turbulent fluid, such as steam, in such a manner that the individual filaments of the yarn are looped, coiled, or crimped and the yarn is heat-set in this condition. The individual filaments are in this manner formed into a bulky wool-like product wherein each of the filaments in a relaxed condition exhibit a plurality of crimps or loops along a given length. These crimps are usually offset and out of phase with each other in a random manner.
One difficulty encountered in these known pneumatic processes is a requirement to provide a sufficient number of crimps to a given length of yarn. Often it is difficult to obtain consistently more than 10 crimps per inch in the filaments of the resulting yarn product.
Many prior attempts to improve the crimp count involve procedures to impinge, fold or coil the yarn in such a manner that the yarn filaments are highly crimped while allowing the yarn to be subsequently removed from the apparatus without loss of desired yarn properties.
Also, the procedures used for separating the yarn from the fluid stream, usually hot air or steam, are important to the success of the crimping process. Various devices such as angled baffles, bulking tubes with reverse exhaust bulking chambers with lateral exhaust ports, rotating screen drums and the like have been employed. The use of such devices often imposes limitations of yarn speed, yarn uniformity or process flexibility on the known processes.
In order to overcome a number of drawbacks attendant to these pneumatic bulking techniques, several developments have been made. For example, U.S. Pat. No. 2,982,082 discloses a process and apparatus for producing voluminous yarn wherein a continuous filament yarn is fed into a jet by a pair of rollers. The jet has an inlet tube extending through a chamber and is provided with a jet tip which faces and enters the mouth of a venturi passage. The outer surface of the jet and the mouth of the venturi cooperate to form an annular passage for a fluid stream under pressure to be blown into the chamber and out through the venturi. The yarn is drawn out of the jet by an additional pair of rollers at such a rate that the yarn is overfed to the jet so that the individual filaments of the yarn are formed into loops and curls by the turbulence of the air stream beyond the annular passage within the jet.
U.S. Pat. No. 3,373,470 described a process for stuffer-type crimping of thermoplastic filaments wherein the filaments are introduced into one end of an elongated confined space by a stream of fluid such as steam under pressure and at a temperature sufficient to set the filaments. The filaments are tightly packed within the confined space by controllable releasing part of the fluid from the confined space laterally of the confined space at a position spaced from the other end and the packed filaments are then forced through the space to the other end under pressure by the remaining portion of the fluid which exhausts with the yarn. The confined space required for this process is defined by a metal spring having gaps between the convolutions thereof. In this apparatus the yarn is propelled by the action of the fluid from a nozzle through a tubular passage and then into the interior of the spring. The spring is curved to a desired extent to obtain optimum packing of the yarn therein.
U.S. Pat. No. 3,380,242 described yet another process for providing a crimp to synthetic yarns wherein the yarn is subjected to the action of a turbulent stream by passing it through a jet to which a hot gas is supplied. The yarn and hot gas leaving the jet enter a venturi tube wherein the individual filaments of the yarn while in a plastic state and under substantially zero tension are separated from each other and crimped individually while whipping about in the turbulent plasticizing stream. The crimp produced by this process has a random three-dimensional curvilinear extensible configuration.
There are still a number of drawbacks, such as uneven or irregular dyeing characteristics, non-uniform crimping and the occurrence of snarls or tangles in the yarn which need to be overcome. For example, in the manufacture of tufted carpets it has been found that tufting machines require particularly uniform yarns and that snarled yarns will cause stoppage, broken filaments and even end breakage. Also, the snarled or tangled yarn will provide faults in the carpet product. Therefore, manufacturers of texturized carpet yarns are continuously looking for apparatus and processes to provide bulky yarns which will dye uniformly and which are free from snarls and tangles.